


Who's IDEA Was This?

by Mrs_SimonTam_PHD



Category: Supernatural
Genre: Angelcest, Being mistaken for lovers, Buddy Cop Drama, Case Fic, Castiel and Lucifer get into shenanigans, Hints of D/s dynamics, I'm sorry I'll leave, Impersonating Security Personnel, Lucifer likes making people uncomfortable, M/M, Polyamory, Pretending to be in a sexual situation for the sake of remaining undercover, Stealing curse boxes, The Casifer Business, jealous!Sam, of sorts
Language: English
Status: Completed
Published: 2018-08-24
Updated: 2018-08-24
Packaged: 2019-07-01 19:45:07
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,600
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/15780828
Author URL: https://archiveofourown.org/users/Mrs_SimonTam_PHD/pseuds/Mrs_SimonTam_PHD
Summary: Castiel and Lucifer have to team up to steal a curse box from a museum. It's like a buddy cop show.





	Who's IDEA Was This?

**Author's Note:**

  * For [madamelibrarian](https://archiveofourown.org/users/madamelibrarian/gifts).



> SO. This is for @madamelibrarian. This could also be BY @madamelibrarian. We remember this was a prompt she had. We just have NO clue if we co-authored it or if I wrote it by myself. Neither of us can figure it out. 
> 
> At this point, it's like "Did she and I write this together?" "Did she possess me to write this?" "Was JFK killed by the Chicago Mob?" "Was Jack the Ripper really Jill the Ripper?" "Does the Mothman Exist?" Like many other cases, it will probably remain unsolved. 
> 
> So M. I love you. Here is a fic that was actually written I think last year.

“This is ridiculous,” Castiel grumbled as he walked next to Lucifer. “Why do we have to do this?” 

“Sam’s laid up with a broken leg, Dean’s being a mother hen, and Gabriel’s gallivanting off to parts unknown,” Lucifer whispered back. “You look good, by the way.” 

Castiel grunted. “ **Flattery will get you nowhere, brother** ,” he grumbled. “ **I look ridiculous** .” 

Lucifer looked his brother over and chuckled softly. “ **I don’t think you look ridiculous. That could be the hair, but we can’t have our unkempt hair with this get-up** .” He nodded politely at the manager as he swiped his keycard to get into the museum. 

Sam and Dean needed a curse box that was in a museum for a case that they were working on (that and they felt it was better to keep all the curse boxes in the Men of Letters bunker), but Sam had broken his leg two weeks ago on a wendigo hunt and was stubborn about being healed. Dean, in the meantime, took it upon himself to mother hen his younger brother. Gabriel, while he cared about his mate, also was busy causing mischief. 

Ridiculous, Lucifer knew, but he and Castiel were the only viable,  _ reliable _ options at this point. 

“ **What is even in this curse box?** ” Castiel grumbled, trying to brush the lint off of his uniform sleeve. 

“ **I don’t know, and I don’t care** ,” Lucifer whispered back. “ **Now stop acting so surly. People will get suspicious.** ” 

“ **We’re already suspicious,** ” Castiel whispered. “ **We’re two guys talking in a language no one knows.** ” 

“ **If anyone asks, take my lead,** ” Lucifer murmured, finding his desk and logging onto the database, Castiel taking the seat up next to him. 

“ **I wish Dean was here** ,” Castiel sighed softly. 

“ **He wouldn’t be able to keep his hands off you, and you’d have to tie him to the bed** ,” Lucifer chuckled, pulling up the video feeds and scanning over them quickly. 

Castiel rolled his eyes. “ **Like Sam and Gabriel wouldn’t do the same to you if you showed up, except you like rolling over for them.** ” There was no venom or judgement in Castiel’s voice, just wry amusement. 

Lucifer playfully nudged Castiel. “ **I look too much like I did when I was a general in Heaven for Gabriel to even think about taking my ass,** ” he said, typing a few lines of code into the computer. “ **Not sure how Sam would react. Probably attempt to hurt himself to try to get to me.** ” 

Castiel snorted a laugh. 

They worked in comfortable silence for a while before a woman’s voice interrupted them. “It’s nice to see a couple working together.” 

Castiel’s cheeks flared red, but Lucifer laughed. “We’re not together, we’re actually brothers,” he said smoothly. 

“Oh!” she blushed. “I’m sorry. I just saw the last names and saw how close you were sitting and the wedding rings and I. . . assumed.” 

Castiel gave an embarrassed smile while Lucifer laughed warmly. “It’s alright. Jimmy has no concept of personal space with family and friends and it doesn’t bother me.” 

Castiel could kill Lucifer. He mimed hitting Lucifer over the head and the woman giggled. 

“So Jimmy’s the younger?” she asked. 

Lucifer smiled at her. “Yes. He’s the baby of the family. Our parents were busy.” 

Castiel snorted. 

“And where do you fall in the line up?” the woman asked warmly. 

“Second oldest,” Lucifer said, leaning over his keyboard. 

“ _ Nick, _ ” Castiel hissed. “Stop flirting. Your husband wouldn’t appreciate it.” 

“I’m not flirting,” Lucifer said innocently. “I’m conversing.” 

Castiel rolled his eyes. “Forgive my brother, he’s a horndog and I still don’t know how his husband hasn’t broken him of the habit,” he apologized. Lying felt weird. But Sam was also a very,  _ very  _ jealous mate. Castiel remembered the last time Sam got jealous. It wasn’t pleasant for anyone (except for maybe Lucifer, who sometimes flirted in front of Sam so Sam would ‘go to town’). 

The woman giggled before sitting down in front of her own computer. “It’s fine,” she said. “Some men like to flirt. I’m okay with it.” 

Lucifer gave a self satisfied smile at Castiel. 

“I’ll admit, both of your spouses are  _ very  _ lucky to have you two,” she added. They both turned to look at her. She shrugged. “What? I’ve got a sex drive. I can  _ definitely _ appreciate the looks. And I might have a mild uniform kink.” She licked her lips. “I wouldn’t mind being in the middle of a sandwich with you two.” 

Castiel turned bright red and coughed. Lucifer just laughed and winked at her. “Fantasize all you want, honey. Could you tell us a little about some of the artifacts here?” 

“Sure,” she said, coming around to the computer screen. It had flipped to a feed of the curse box and she shuddered. “That thing gives me the fucking chills. I don’t like it.” 

“Why not?” Lucifer asked calmly. 

“Whatever’s in there is  _ not  _ pleasant,” she explained. “It just. . . It creeps me out. I’ve been trying to translate the symbols on the side when I’m not doing legal research, and as far as I can tell, there’s a cursed object inside. One that harbingers death and destruction. I can’t recognize all the symbols though. It’s been in the museum for about thirty years. I’ve been here alone with it, and I  _ swear  _ it talks.” 

Lucifer and Castiel arched twin brows. 

“I know, it sounds crazy,” she laughed, “And it’s probably an overactive imagination combined with too many horror movie marathons with friends and Jaeger. But I’ve heard it whisper in. . . Well, I’m going to assume it’s a dead language. I’ve never heard it before, and I like to listen to foreign languages. Helps me work.” 

Lucifer nodded, wondering what was in the curse box. 

 

It was several hours before Lucifer and Castiel could even get up and near the curse box without anyone being suspicious. The only one in the building at three AM was the woman who mistook them for a couple before, and she had headphones on and seemed engrossed in whatever was on her computer. 

They moved out onto the floor to the museum, after much hushed bickering in Enochian as they played a loop of the curse box feed into the mainframe, so no one could tell they were stealing it. 

They approached the glass and Lucifer went to work disarming the alarm system, Castiel keeping a look out. 

“Hurry up,” Castiel hissed, straightening his uniform yet again. It was almost as if he was preening. 

“Do you want to do this?” Lucifer snapped. “One wrong move and I’m going to lock us in and get us thrown in jail. And Sam and Dean won’t be happy about that.” 

Castiel rolled his eyes. “We could just snap out of there, idiot,” he said. 

“It’s the  _ principle _ of the matter, Castiel,” Lucifer groaned. He finally disabled the system. “Okay, I disabled the alarm system. Let me lower the heat sensors so we can snag this. And I think there’s going to be an invisible laser field.” 

“Remind me why we’re not using our powers for this?” Castiel asked, starting to pace nervously. 

“Stop pacing,” Lucifer groaned. “And because it’d leave too wide of a kinetic energy field that has our signatures in neon signs and we want to be below the radar so we don’t spook the demons into being idiots.” 

Castiel sighed over dramatically before tensing. “Somebody’s coming.” 

“ETA?” Lucifer asked. “Heat systems down. Give me a couple more minutes for the laser field. Then you can remove the glass.” 

“They’re about half a minute out.” Castiel sounded worried. 

“Go distract them,” Lucifer instructed. “Say you needed to stretch your legs  and decided to do a perimeter check.” 

Castiel rolled his eyes but did as he was told. 

Lucifer turned his angel ears on and listened in. 

“Hello, Novak, didn’t expect to see you up and about.” 

It was the night manager. Lucifer stuck his tongue between his teeth as he worked on the laser field, grateful he spent hours with Sam learning how to disarm systems. 

“Needed to stretch my legs, figured I’d do a perimeter check,” Castiel lied smoothly. 

“Where’s your brother?” the manager asked. 

He could  _ feel  _ Castiel’s eyeroll. “I swear that man could sit for hours on end. I don’t know how he does it. It’s just unnatural.” 

The manager laughed. “Well, I’m just gonna duck into my office. Try to convince him to get up. He doesn’t want to get clots in his legs. That’ll kill him faster than anything.” 

“I’ll let him know, but no one makes Nick do anything,” Castiel sighed dramatically. “It’s as if he thinks he’s king of the world. I swear, he’s more stubborn than a mule.” 

_ I’m going to leave you in a ring of holy fire when we get home, baby brother, _ Lucifer thought sourly as the night manager roared with laughter. 

“I kind of got the ‘stubborn’ vibe from him,” he said. 

“You have no idea,” Castiel said dryly. “Have a good night, Sir.” 

“You too, Novak.” 

_ Put me in holy fire all you want. I’m circling around and coming back. Night manager’s a demon.  _

_ Fuck. _

_ I TOLD YOU THIS WOULD BE EASIER WITH POWERS.  _

_ HOW?! WHY HAVEN’T YOU KILLED THE MANAGER YET?! _

_ NOT EVERYTHING NEEDS TO INVOLVE KILLING, LUCIFER.  _

_ I WOULD SAY THIS IS AN EXCEPTION TO THAT.  _

_ Whatever. I’ll be there soon. Hurry up with the disablement, old man.  _

_ Fuck off, young whippersnapper. _

Lucifer finished undoing the wiring for the laser field and he stood up, dusting his hands off before sliding on the thick, black leather gloves and removing the glass surrounding the curse box and carefully picking it up. 

Whatever was in here, the legal researcher was right to be wary of it. Lucifer recognized binding spells of all sorts on it, and there was a definite whisper. 

“Hurry the fuck up,” Castiel hissed from behind him. “You can admire the pretty box at home.” 

“Bossy little brother,” Lucifer grunted, handing the box to Castiel before pulling one that was similar to what was being held in the seraph’s hands out of thin air. He put the fake curse box there and placed the glass around it again. 

“Can we  _ go  _ now?” Castiel sounded like a whiny child. 

“I have to put the security systems back online, Castiel,” Lucifer hissed, dropping to the floor again. “Otherwise, it’s going to look suspicious.” 

Castiel sighed and tucked the box under his arm. “And what are we supposed to do if the night manager comes out? Or someone else?” 

Lucifer shrugged. “Give me a warning and who it is and I’ll think of something,” he grunted, starting with the laser field first. It was the worst of the security systems. “Set the box down, near me, and put an invisible thingy around it.” 

Castiel rolled his eyes but did as he was told. “I’m afraid of what your backup plans are.” 

“Why be afraid?” Lucifer asked, concentrating. 

“Because you’re highly creative,” Castiel hissed. 

“Don’t worry about that,” Lucifer said dismissively. 

Castiel tensed again. “Someone’s coming.” 

“Who?” Lucifer asked irritably. He still had the heat sensors and the alarm system to redo. 

“Someone new. Legal researcher is too busy reading. . . why is she researching cannibalism laws in Idaho?” 

“Beats me, boredom probably,” Lucifer grunted. “Night manager?” 

“Eating Cheetos and watching pornography.” There was a note of distaste in the seraph’s voice. 

“Okay, that helps,” Lucifer said. “Just go along with what I’m doing, alright?” 

“What are you-” Castiel’s voice was cut off short by Lucifer nuzzling his crotch. How his older brother managed to go from laying down and concentrated on the systems, to on his knees, looking absolute cottequish was beyond him. 

Castiel fisted Lucifer’s hair and made his brother look up at him. There was that devilish smirk that Castiel both loved and hated. Right now, it was in between. “Gonna be a good boy for me?” the seraph asked the archangel, licking his lower lip. 

Lucifer batted his lashes up at Castiel. “Aren’t I always a good boy for you, Sir?” he breathed. 

Okay, maybe Castiel could see where Sam was coming from in topping the archangel. Lucifer was looking. . . well, he was looking like Dean when Dean was being particularly subby. Full pout, pleading eyes, eagerness in the voice. “You do your best,” he murmured. “Don’t like doing this at work, you know.” 

“But it’s been  _ so long  _ since I’ve had your thick cock in my mouth,” Lucifer whined, rubbing his nose against Castiel’s length. “Wanna taste it. Please, Sir? Let me swallow you down?” 

Castiel closed his eyes briefly. “Not right now.” 

The footsteps stopped near them, as if waiting. Both of them tested to see if it was a demon, and found no traces of demonic possession in the man. 

“But  _ Sir, _ ” Lucifer whimpered. “Want you to fuck my mouth.” 

“Greedy little sub, aren’t you?” Castiel groaned. “I said  _ no. _ ” 

“But  _ Daddy, _ ” Lucifer whispered. “You need it.” 

Oh, Lucifer was playing dirty. Castiel hated and loved him for it. 

The footsteps hadn’t moved, but there was only a matter of time.

“I  _ said,  _ no, Nick,” he said more firmly. “Ask me one more time, and I’m bending you over and taking my belt to your ass right here.” 

Lucifer gave a full bodied shiver at that, one that Castiel wasn’t sure was faked, before nodding. “Please?” 

The footsteps hastily retreated as they heard Castiel’s belt buckle clank against his keys, and Lucifer smirked as he fell back onto his back, returning to work. 

Castiel scowled at his crotch and his brother. “ _ Really? _ ” 

Lucifer shrugged. “Sex makes people reconsider paths,” he said. “And I figured if I could bring out that Dom voice, it’d  _ definitely  _ spook them off. And I was right.” 

Castiel hastily redid his belt. “I’m telling Sam,” he informed him. 

“It’s for the case, and I wasn’t  _ actually  _ going to suck you off,” Lucifer said, finishing the heat sensors and working quickly on the alarm system. 

“I was serious about beating your ass,” Castiel grunted. “Now, please,  _ hurry up. _ ” 

“Done.” Lucifer stood up, scooping up the box. “I still think we should take care of the demon.” 

“Leave the demon alone,” Castiel growled. “The death would look suspicious.” 

Lucifer sighed. “You’re right. Okay. Fine. I won’t kill the demon. Can I just-” 

“ _ No. _ ” 

“You’re no fun,” Lucifer grumped. “Fine. Let’s get out of here.” 

They teleported out, no one the wiser. 

 

They arrived at the bunker, Lucifer triumphantly holding the box high above his head. They were both still dressed in the security guard uniforms, and their mates’ eyes were bugging out of their heads. 

“Um. I’m turned on,” Sam breathed, swallowing. 

Dean licked his lips, staring at the handcuffs on Castiel’s belt as Gabriel slid up to Lucifer and began kissing his neck. “Please wear this more often,” the younger archangel said. 

“Yes, dear,” Lucifer smirked. 

“By the way,” Castiel looked at Sam. “You have a bratty sub.” 

Sam laughed. “I knew that. What did he do?” 

“Flirted with a legal assistant and propositioned me with a blow job. Called me Daddy, too,” Castiel said with a shrug, a devilish smirk not unlike Lucifer’s spreading across his face. 

Sam’s eyes darkened as he looked over at Lucifer. “Oh did he, now?” 

“It was a distraction!” Lucifer defended himself. He looked at Sam. “Baby, you know I love you, right?” He kneeled next to Sam and rested his head on his thigh. “I love you and Gabriel, and I wouldn’t cheat on you two with Castiel.” 

“ _ Hey! _ ” 

Some things never changed. 

**Author's Note:**

> Find me on tumblr! @lucibae-is-dancing-in-hell.tumblr.com
> 
> Comments and Kudos are Shiny!!


End file.
